1. Field of the Invention
The present invention relates generally to liquid, polymerizable vinyl or vinylidene monomer containing compositions stabilized against premature polymerization. More particularly, the invention relates to a composition containing a vinyl or vinylidene monomer capable of free radical polymerization and a biphenol derivative having the following general formula: ##STR2## wherein R' is hydrogen or an alkyl group containing from 1 to 4 carbon atoms,
R.sub.1, r.sub.2, r.sub.3 and R.sub.4 are alkyl groups containing from 1 to 5 carbon atoms, and PA0 R.sub.5, r.sub.6, r.sub.7 and R.sub.8 are hydrogen or alkyl groups containing from 1 to 5 carbon atoms provided that only two of these substituents may be a secondary or tertiary alkyl group. PA0 R.sub.1, r.sub.2, r.sub.3 and R.sub.4 are alkyl groups containing from 1 to 5 carbon atoms, and PA0 R.sub.5, r.sub.6, r.sub.7 and R.sub.8 are hydrogen or alkyl groups containing from 1 to 5 carbon atoms provided that only two of these may be a secondary or tertiary alkyl group. PA0 R.sub.1, r.sub.2, r.sub.3 and R.sub.4 are alkyl groups containing from 1 to 5 carbon atoms, and PA0 R.sub.5, r.sub.6, r.sub.7 and R.sub.8 are hydrogen or alkyl groups containing from 1 to 5 carbon atoms provided that only two of these may be a secondary or tertiary alkyl group. PA0 3,3',5,5'-tetramethyl-4,4'-biphenol, PA0 3,3',5,5'-tetramethyl-4,4'-biphenol monomethyl ether, PA0 3,3'-dimethyl-5,5'di-t-butyl-4,4'-biphenol, PA0 3,3',5,5'-tetra-sec-butyl-4,4'-biphenol, PA0 3,3'5,5'-tetra-t-butyl-4,4'-biphenol, PA0 3,3',5,5'-tetraisopropyl-4,4'-biphenol, and PA0 3,3'-dimethyl-5,5'-diethyl-4,4'-biphenol. PA0 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol, PA0 2,2',3,3',5,5'-hexaethyl-4,4'-biphenol, PA0 2,2'-diethyl-3,3',5,5'-tetramethyl-4,4'-biphenol, PA0 2,2'3,3'-tetraethyl-5,5'-di-t-butyl-4,4'-biphenol, PA0 2,2',3,3',5,5',6,6'-octamethyl-4,4'-biphenol, PA0 2,2',3,3',6,6'-hexamethyl-5,5'-di-b-butyl-4,4'-biphenol, PA0 2,2',3,3',5,5',-hexamethyl-6,6'-di-t-butyl-4,4'-biphenol, PA0 2,2',3,3'-tetramethyl-5,5',6,'-tetraethyl-4,4'-biphenol, and PA0 2,2'-diethyl-3,3'-dimethyl-5,5'-di-isopropyl-6,6'-di-t-butyl-4,4'-biphenol. PA0 (a) liquid at room temperature, PA0 (b) capable of free radical polymerization to yield high polymer, and PA0 (c) capable of dissolving the biphenol derivative in the amounts indicated above. PA0 A is a radical derived from a polyoxyalkalene bisphenol having the following formula: ##STR8## wherein R' is an alkylene group, PA0 X is halogen or methyl, PA0 a is an integer equal to from 0 to 2, and PA0 m and n are integers each of which is equal to at least 1 and the sum of which is equal to from about 2 to about 6; PA0 M is a radical derived from an unsaturated, aliphatic, dicarboxylic acid or an anhydride thereof; PA0 I is a radical dervived from a diisocyanate, PA0 B is a radical derived from a hydroxy-terminated ester of acrylic or methacrylic acid; PA0 y is an integer equal to from 1 to about 5; and PA0 R is selected from the group consisting of hydroxyl, I and I-B, wherein I and B are as defined above.
2. Description of the Prior Art
Vinyl and vinylidene monomers useful in the preparation of polymeric materials and a variety of polymerizable compositions containing said monomers are well known in the art.
It is, of course, essential that any monomer-containing composition be stable when stored and that it not undergo premature polymerization during the time from preparation of the composition to that at which it is used. To accomplish this a variety of additives, generally referred to as polymerization inhibitors, have been suggested for inclusion in the composition. These have included, for example, t-butyl catechol, hydroquinone and derivatives thereof such as toluhydroquinone, mono-t-butylhydroquinone, 2,5-di-t-butylhydroquinone and hydroquinone monomethyl ether. However, these materials are often of limited solubility in the monomer employed, or are either volatile or thermally unstable at the elevated temperatures employed in the preparation of the polymerizable compositions in which they are used. To overcome these difficulties it is often necessary to employ mixtures of two or more inhibitors to produce the desired result. It would, therefore, be desirable to have a polymerization inhibitor which could be readily dissolved in the vinyl or vinylidene monomer containing composition a the concentration required to inhibit polymerization of the monomer and which would possess a high boiling point to minimize loss of the inhibitor from compositions which are prepared at elevated temperatures.
To be acceptable as a practically useful polymerization inhibitor, a material must satisfy at least two essential criteria. First, the material must be capable of preventing premature polymerization of the monomer-containing composition in which it is to be utilized. Secondly, when the material is incorporated in a composition which is intended to be polymerized when it is used, it is essential that the inhibitor used not adversely affect either the cure characteristics of the composition or the properties of the polymeric material prepared therefrom. As is well known to those skilled in the art, while there are a variety of materials which will satisfy the first of these criteria, the number of available additives which will satisfy the second criteria is much lower.
Many biphenols and derivatives thereof are known in the art and have been suggested for use in a variety of applications. Thus, U.S. Pat. No. 2,479,948 issued to Luten et al., U.S. Pat. No. 2,785,188 issued to Coe, and U.S. Pat. No. 3,631,208 issued to Hay, disclose that biphenols, including a variety of alkyl derivatives thereof, are useful as stabilizers to prevent oxidative degradation of a variety of materials including petroleum distillates such as cracked gasoline, lubricating oils and hydrocarbon polymers; animal oils; fish oils; synthetic cellulose derivatives; polymers of unsaturated materials; fats; oils; soaps; and aromatic amines. Also, in U.S. Pat. Nos. 3,720,721 and 3,748,303, both of which are issued to Becker et al., it is disclosed that some halogenated tetraalkyl biphenols can be used as antioxidants for petroleum products and as stabilizers against polymerization of monomeric materials to maintain them in the essentially unpolymerized state until such time as they are ready for polymerization.
Several additional references also disclose the use of various biphenols as antioxidants for organic compounds. See, in this regard, U.S. Pat. Nos. 3,153,098 and 3,251,801 both of which are issued to Boag; U.S. Pat. No. 3,247,262 issued to Kaeding; U.S. Pat. No. 3,383,395 issued to Schmukler; U.S. Pat. No. 3,562,338 issued to Zaweski; and U.S. Pat. No. 2,905,674 issued to Filbey.
It has now been discovered that certain biphenol derivatives are especially useful as polymerization inhibitors in compositions containing a vinyl or vinylidene monomer capable of free radical polymerization.